Dreamcast controller port board

I bought a dreamcast with a faulty controller port board recently, it would seem that only port 2 works, none of the others. The LED comes on and it seems to keep the time & date. So I was wondering if anyone has any idea how I might fix this? It also looks as though the F1 fuse has been replaced. It's fine if it can't be done because I have a spare controller board anyway but it seems a shame to let it go to waste unless it's genuinely ruined